The druids are dead, and when they died off, so too did all of their secrets because they never wrote anything down. The only reason we have a vague idea of what they did is due to outsiders witnessing/observing them and then recording down what they saw.

Anyone who claims they are a druid is a neopagan reconstruction of what people feel the druids would be like. But there is no certainty in that.

If you are interested in Irish magick, then I would suggest investigating traditional irish Witchcraft and the mythologies surrounding the culture. The druids were very highly regarded in their society. They were upper class and highly revered. The Irish witches were your everyday common folk, but Irish Witchcraft was still built around the same society, religious beliefs, and time period the druids stemmed from. In my opinion, that is the closest you'll ever come to true druidity--by taking Traditional Irish Witchcraft and placing a shamanic spin to it, as well as reading what was observed from the druids by outsiders (taking into consideration possible misinterpretation of intentions and meanings).

If you are interested in learning more about Druids both ancient and modern there are a few books that I'd recommend:

"Blood and Mistletoe" by Ronald Hutton
"The Druids" by Peter Berresford Ellis
"Druids" by Barry Cunliffe

One of the problems we have in trying to reconstruct the original religion practiced by the Druids is that theirs was an oral tradition and none of it was written down. When the Druids were largely destroyed by the Romans and later replaced by Christianity the beliefs and practices were largely lost. What little we know comes through the writings of men such as Julius Caesar and has to be considered tainted by the fact that largely these accounts were written by individuals who were hostile to the Celts and their Druid priests.

Modern Druidry is an attempt to recapture the flavor of ancient practices but is generally not particularly ancient in flavor. Modern Druids tend to ascribe to practices found throughout Wicca and other Pagan paths. But if you are interested in reading more about modern Druidry I'd suggest the following:

"The Druidry Handbook: Spiritual Practice Rooted in the Living Earth" by John Michael Greer

Druidism is a discipline of earth and nature.Druids are the sacerdotes of nature and 3 of her elements,air,earth and water.In principle,a druid is someone who is one with the nature.Druids have empathy with animals and plants.
Train alot in the disciplines of:Aerokinesis,Hydrokinesis,Geokinesis,Empathy and Alchemy and there you are.